DE2139520A1 - Finely ground mineral agglomerates and processes for making the same - Google Patents

Description

Agglomerates from finely gemafef-enetq mineral and process for the production of the same

Priority: 7/8/1970 - Australia

The invention relates to new compositions of matter, those made from a finely ground mineral and a high molecular weight, essentially straight-chain, water-soluble one Polymer consist, and on a process for the production of agglomerates from such compositions, these Agglomerates have improved properties.

It is customary to use certain finely ground minerals, such as s »B. Iron ores, to agglomerate so that the material can be easily transported and processed. The agglomerates are produced by first moistening the finely ground mineral bit of water, whereupon the moist material is processed into agglomerate bits of a suitable size and shape. The agglomerates are then

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hardened by heat.

Such agglomerates have two disadvantages: 1. The strength of the agglomerates is often not high enough that the Agglomerates disintegrate during handling. 2. When heated, the agglomerates can also disintegrate, namely with- ' for example because of a lack of physical strength or because of a sudden uncontrollable release of free or bound moisture. Such uncontrollable or explosive release of moisture is of course undesirable and leads to production losses «In order to eliminate these difficulties, it is common practice, for example in the pelling of iron ore, to add hydrated lime or bentonite to the finely ground mineral before agglomeration However, the method is not always acceptable, as the additives typically in to achieve a sufficient effect Concentrations of about 0.5 wt% based on the fine ground material, must be present and this required leads to greater difficulties in handling the Lead raw materials. Furthermore, such large amounts add significantly to the overall processing cost. Another disadvantage in the case of metal-containing materials is that, as a result, they are relatively large Additions reduce the metal content of the mineral agglomerates, which leads to a reduction in the effectiveness can result from subsequent extraction processes *

It has now been found new compositions of matter from which agglomerates can be produced that these Do not have disadvantages *

Thus, according to the invention, agglomerates are proposed which consist of a finely ground Hineral, an effective amount consist of a high molecular weight, largely straight-chain, water-soluble polymer and water.

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According to the invention, a method for producing agglomerates is also proposed, which thereby is carried out that one finely ground mineral with an aqueous solution of an effective amount of a high molecular weight, largely straight-chain, water-soluble Folymezs are mixed and the resulting mixture is treated to produce agglomerates.

By the term "high molecular weight" is a molecular weight

from 500,000 to 25,000,000, preferably from 1,000,000 to 20,000,000, meant. While it is preferred that the polymers be straight chain, there is a small proportion of branched chains in the Polymers can be accepted * Under the scope of

The invention also includes polymers that contain such small amounts of branched chains.

Examples of suitable polymers are polyacrylamide and polyacrylonitrile and polymethylacrylamide. Suitable polymers are derived from ethylenically unsaturated monomers, e.g. Acrylamide, acrylonitrile and methyl acrylamide. Mixed polymers, obtained by copolymerization of acrylamide, acrylonitrile or methacrylamide are also suitable * According to the invention, the alkali metal · or Alkaline earth metal salts of the polymers can be used.

It has been found that other high molecular weight polymers are also suitable according to the invention, e.g. Polyalkoxylates obtained by condensation of ethylene oxide, Propylene oxide or butylene oxide or mixtures thereof with water, alcohols or phenols can be obtained.

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The high molecular weight »essentially straight-chain, water-soluble polymers used according to the invention, water-soluble polyelectrolytes. With the The term "polyelectrolyte" is intended to mean a polymer made with substituted by a number of ionic groups. Such are preferred polymers for use in accordance with the invention for example polyacrylic acid; Polymethacrylic acid; Mixed polymers of acrylamide, acrylonitrile or methacrylamide with acrylic acid or methacrylic acid; Sodium salts of copolymers of maleic acid with, for example, styrene or methyl vinyl ether; the sodium salt of carboxymethyl cellulose; synthetically modified starch polymers such as a starch grafted polyacrylonitrile; Polymers that contain amino groups such as polymers of dimethylaminoethyl methacrylate; and polymers containing quaternary ammonium groups.

These polymers can be prepared by any suitable method known in the art.

The polymers described above can give a highly viscous solution in pure water. Such a solution can, in some circumstances for use in a conventional apparatus, such as si _(e example, is used for pelletizing iron ore may be unsuitable '; However, the viscosity of such aqueous solution by the addition of inorganic salts such as sodium chloride. , Sodium sulphate or potassium chloride, natural saline waters can also be used, such as seawater or groundwater * This is an economic advantage if the process is carried out in an area where only saline water is freely available.

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Appropriate amounts of polymer that will give satisfactory results, are between 0.0005 and 4.5 kg per ton of finely ground Ore or mineral. It is preferably 0.005 to 2.3 kg and especially 0.009 to 0.9 kg of polymer per 1 ton of finely ground mineral to use *

The polymer is conveniently dissolved in the water used for mixing with the finely ground material. For example, a polymer concentration in seawater is of 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight, suitable, using the water spray system of a conventional pelletizer with inclined rotating disc used, for example the Dravo Pelletizing Disc Equipment such as her is used in the manufacture of iron ore pellets »

When agglomerates «by the inventive method described above Processes have been made to be cured by heating in an oven, then the degree of dissolution lower, which is caused, for example, in a lack of physical strength or a sudden uncontrollable release of eggs or bound moisture Has.

So Sottrd an improved method according to the invention proposed for the production of hardened agglomerates, which is carried out by first forming an agglomerate from a mixture that consists of a finely ground material, a high-molecular, largely straight-chain, water-soluble polymer and water, and that the agglomerate is then hardened by heat treatment.

The intensity of the heat treatment required to harden the agglomerates depends primarily on their nature of the agglomerates from »In general, the normal one is suitable

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Heat treatment necessary for hardening common agglomerates or pellets (not according to the invention) is required. For example, pellets made from finely ground iron ore can be hardened by slowly removing the pellets Room temperature to a temperature in the range of 1200-135O ° C heated, in a usual straight host for iron ore pellets, in a grate furnace or in a shaft furnace.

The invention can be used to produce agglomerates from one finely ground material can be used. For example, it can be used to make briquettes from coal dust of bricks, especially refractory bricks and ceramic products, and also for the production of pellets made of finely ground ore, such as iron oxides, copper oxides, barytes, lead and zinc sulfides and nickel sulfides will"

The invention can also be used to produce composite agglomerates, such as those comprising a Mineral, a slag-forming additive and a reducing agent contain * Such compound agglomerates may be used as feed for melting processes

A suitable size range for the metal-containing ores and minerals which are used according to the invention is between 10 and 1000i £, preferably between 20 and 300 / yr.

The invention can also be used to produce catalyst pellets and supports for catalysts. Another embodiment is the production of fertilizer granules.

The invention will now be further elucidated by the following examples in which all parts are expressed by weight.

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Beis p iel Λ

Dissolving polymers in sea water were carried out as follows Process produced *

5 parts of polymer were added to 995 parts of filtered seawater. »The polymer was carefully moistened with the seawater, "before stirring was started. The mixture was agitated using a slow-speed mechanical stirrer, until essentially all of the polymer was dissolved. This solution was used as a pelletizing aid in manufacture of iron oxide pellets from Hamersley pelletizing feed used.

The Hamersley Pelletizing Charge is a finely ground iron ore of the hematite type (approximately 63% Fe) with a Blaine Index of 2,500 to 2,700. This polymer solution was diluted with sea water to give a polymer concentration of 0 _t 1 wt cm located. In this way, pellets were prepared in the mm size range of 6.3 to 9 _5. 5 The disk was inclined at 52 ° and rotated at 24 rpm. Comparative pellets were prepared in a similar manner (a) in the absence of a pelletizing aid and (b) using 0.5% bestonite as the pelletizing aid. The uncured pellets were examined for pelletizing aid and water content. The average burst strength of the uncured pellets prepared using each pelletizing aid was measured in a conventional burst strength tester. The average drop resistance of uncured pellets was measured by determining the average number of times the pellets were taken from a height of 18 inches

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could be dropped onto a hard surface without cracking. Were the apparatus used for measuring the drop strength consisted of a series of 6 small boxes ♦ with automatically opening, held by a spring floors equipped "The pellets fell 45 ₁ 7 cm wide on a polished steel plate" Six pellets could simultaneously reproducible Conditions to be dropped *

In an initial experiment, pellets made from Hamersley pelletizing feed without a pelletizing aid were cured. It has been found that the strongest Zerbröcklen the pellets occurred in a temperature range of 290-460 ⁰ C. Negligible dissolution occurred on heating to temperatures above 550.degree. In order to demonstrate the effect of the pelletizing aid on the comminution of the pellets, it was only necessary to partially harden the pellets by heating them to 55O ° C *

Samples of the pellets prepared above using each pelletizing aid were taken partially hardened by slow heating to 55O ° C. The weight percentage of fine material peeled from the pellets during this partial cure was determined measured in that the partially hardened material was passed over a sieve with a mesh size of 3.2 mm and the obtained fines were weighed.

The results obtained with the pellets obtained using the various pelletizing aids are shown in Table 1.

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Table 1

co OO

ro

Pelling kg of pellets Weight # average average Weight # Tools sierungflhiIfa
medium per sun
Iron oxide Damp
ability in
Pellet lich bursts
strength
(kg) lich case
strength Fines,
the during
of heating
were formed nothing 7.5 1.1 2.5 2 Bentonite 4.99 7th 1.4 4th 1 Polymer 1 * 0.12 8th 1.6 8.0 0.1 Polymer 2 ** 0.12 7.5 1.8 12th 0.05 Polymer 5 *** 0.12 8th 3.2 12th 0.08

Polyacrylamide, approximately 2% hydrolyzed, molecular weight approximately 5,000,000
2: 1! Fish glymer of acrylamide and sodium acrylate with a molecular weight
ύοώ. approximately 3 000 000
straight chain polyethylene oxide with a molecular weight of approximately 10,000,000

- ίο -

Example 2

In a further series of tests, the four mixed polymers A, B, C and D listed below were used as agglomeration aids, including pellets (i.e. agglomerates) of iron oxide * The polymers used are shown in Table 2.

Act 2

A 2: 1 ~ mixed polymer of acrylamide and sodium acrylate with a molecular weight of approximately 5,000,000

B 12: 1 copolymer of acrylamide and sodium methacrylate with a molecular weight of approximately 9,000

1: 1 partial polymer of acrylamide and Sodium acrylate with a molecular weight of approximately 5,000,000

B cationic copolymer of dimethylaminoethyl methacrylate and acrylamide with a molecular weight of approximately 9,000,000

The iron oxide samples used in these experiments had the analysis shown in Table 3.

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Table 3 Thermogravinetriache, chemical and sieve analyzes of the ore

thermogravimetric data (10 ° C / mia)

Loss of free water 21 - 177 ° C 0.46% Water loss of goethite 177 - 416 ° C 2.20% Water loss of the kaolinite 416 - 600 ⁰ C 0.68% G0 ₂ -7 loss of limestone 600 - 900 ⁰ C 0.54%

total weight loss 21 - 900 ° 0 3 »88%

chemical analysis (dry basis)

total Fe 62.0%

SiO ₂ 3.9%

Al ₂ O ₃ 2.3%

CaO 0.58%

wet sieve analysis (mm)

+ 0.214 3.60%

- 0.214 + 0.125 7i72%

- 0.125 + 0.066 18.00%

- 0.066 + 0.053 4.74%

- 0.053 + 0.042 3.34%

- 0.042 62.60%

Green pellets (i.e. agglomerates) were prepared from the ores in the following general manner, one being 1 m Head Wrightson disc pelletizer was used. Dry Ers was continuously coming out a Syntron vibratory hopper feeding unit suge ~ and the required amount of seawater or polymer / seawater solution was introduced through spray nozzles.

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The green pellets coming off the disc were on a mechanically shaken Denver wire mesh, and the product, which was smaller than 15 * 9 mm but larger than 9i5 »m, was used to measure the properties of the pellets and in the grinding tests.

The bulk density, the pellet density, the compressive strength, the Drop strength, the temperature at which the agglomerates crumbled due to leakage, and a simulated one The rust rate for hardening the agglomerates was determined in the following manner.

Measurement of bulk density

The bulk density of each batch was determined by weighing a known volume of the pellets (14 liters).

The density of the pellets was also determined by plotting the volume of a weighed pellet sample in Kerosene (specific gravity 0.782 g / csr) was measured in a volumetric flask. The values obtained are given as pellet density and are a better "ate for the pellet porosity and the bulk density"

Measurement of compressive strength

The formation of homogeneous samples on the disc was ensured by continuously increasing the strengths the pellets on a simple compressive strength tester were determined. More detailed statistical measurements of the compressive strength of the product were then made below Using a Showa control device carried out. In this device, a 5 kg load cell was used to determine the strength of green pellets and tine Cell loaded with 500 kg for testing fired cells

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Pellets used. The device was operated at a constant closing speed of 12 mm / min. In each Case were pellets with 12.7 ί 1 s » selected.

Measurement of the drop strength of the

Green pellets were dropped from a height of 45 »7 ® m onto a ® steel plate to test their ® impact strength. For each batch, 10 pellets with a size of 12 _s were dropped 7 ± 1 s® msM times 50 times. The gradual Zesfcleisitru & g was buoh-led ":

Limited hours ung _ι of, pgg

The determination of the Serkleiserungsteiiper & ttar © ia®3? each batch of pellets was carried out using a plant simulator developed at OSHft-Maaral-Iefeoratoriee in Ejde. The fixed drive "sur Mee" ung DCIV "Wärseempfiadlichkeitteiiperatur ⁿ ia a ¥ isg © bwig d \ ir © _hg®führt? In a controlled © temperature and ice. Wind prevails. Ss klein® batches (20 used up pellets" She @ aeg @ äohwimäigl £ @ it wuM @ so that the © Serkiäinsru ££ dfr 7 @ 13, @ t @ which was the same as it was in the upper ^ S bm © in @ s Bettm sit v @ ll @ occurs. "read unte ^ si®uli # ^ feas Aslagabediaguag ^ a is the sample au © 20 to 25 Pallete was in wire basket in dw column a% & fgeh &agt" consecutive Torsuohen were Tuven the feaper & eat changed; to the Tecro ^ FTTU? BU eraittsl ^, at d ^ .d & a free waes # r a «comminution revwffe & Qht , deh» dl® T ^ EEperatur «dia in a pellet coffin * 1 to 5 comminution ·» dti? 6 & Wasaer * »causes leakage»

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Simulated system speed wind speed

The peel temperature profile was determined, one Maximum grate speed (and thus production) allowed without substantial size reduction. It became the same Column as used for heat sensitivity measurements, but a full bed was examined * It an operation was simulated old upward draft and downward draft, and the gas flow rate was regulated depending on the pressure drop in the bed. The first investigation was in a glass pot simulator so that the bed of pellets could be observed during drying and firing. The data obtained with the glass pot were made using a "Hot Body Pot" verified to be low thermal To simulate loss conditions of a normal plant »

Glass pot: A 7 * 6 cm wide column of Pyrex glass was used. The depth of the bed of green pellets was 40.6 cm above a 10.2 cm thick hearth layer of pre-burned pellets. The bed depth corresponds to the practice in a plant the draft conditions that can be achieved in a fcander grate / windbox environment of an industrial plant. The sequence simulates the movement of the bed along the wandering host «

"Hot body pot": The glass pot of the column was replaced by a steel chamber lined with refractory kaolin fibers. 7.6 cm diameter replaced. This can be operated at temperatures up to the firing temperatures. The thermal losses from the hot body simulator

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are sufficiently low that the time / Temperature profiles «that are generated in this simulator, are the same as those produced in a 35.6 cm pot grid simulator. The results of the experiments are shown in Table 4 ·.

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- 16 Table 4

Results of the heat sensitivity measurements

Attempt number 1 β 221 I. 2 3 4th 5 6th 7th co _ü mm Pelletizing A. S- - B. B. B. mm σ D. tools Concentration (kg / - Ton of burnt
Pellets) 0.14 0.14 0.14 0.07 zero zero 0.14 Q,; i4 218 Feeds dizzy ■ ".. · of the ore 228 228 228 _- - Disc (kg / st) green * pellets - Humidity (%) 8.1 7.8 8.0 7.6 7.4 7.5 9.4 3.3 Density of * Pellets CgZCm **) 3.54 5.66 3.52 3.54 3.54 3.62 3.47 5.32 Bulk density (P, CP.) 133 131 132 129 132 137 127 138 Strength (kg /
Pellet) 2.7 4.1 4.8 2.9 2.5 2.7 1.9 4.0 Fall down - fall up sum
first 30th 30th - - - 26th 30th fracture "- fractions at 30- 0 0 «Μ mm Ma 2 0 malignant case Strength of the burned pellets «Ρ» 324 307 306 (kg / pellet) Temperature of the cer downsizing through free " Water 221 232 221 193 193 243 light temperature) ⁰ C Änlagenrostge dizzy
ability (sec / windbox) - 33 30th 45 45 27 relative · productions speed 137 150 100 100 167 (without addition - 100)

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The Abangstemperaturprofile _t in the experiments 3 ₅ 4, 5 were determined "and 7, the maximum -am Anlagenrostgesehwiadigkeit allow 3u, are shown in Table 5."

Table 5

7 search number 3 4th 5 6th 7th Plant grate geachwin-
age (sec / wind box) 33 30th 45 45 27 Withdrawal temperature profile 11 * Windbox iTuiaiaar 1 121 121 121 121 121 2 171 143 171 171 171 3 210 182 177 177 182 4th 221 204 Ί82 182 193 CO
CVI 216 188 188 204 6th 249 216 193 193 216 7th 260 216 199 199 227 8th 277 271 227 227 279 9 249 221 193 202 260 10 210 199 166 177 238 11 210 199 166 177 238 12th 238 204 182 188 238 15th 277 227 193 199 249 14th 321 271 204 221 268 15th 371 310 238 274 299 16 516 354 310 327 360 17th 432 382 399 416 410 18th 449 399 432 432 477 19th 521 482 449 449 566 20th 621 566 560 558 659 21st 720 659 671 671 760 22nd 871 871 871 871 871 ' 23 871 871 871 871 871 24 1371 1371 1371 1371

♦ Wijadboxes 1-7 downward draft "■" 8-18 upward draft

43 % 2 cm wg 43 _f 2 cm wg 5 em wg

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Example 3

This example demonstrates the effect of aqueous solutions of polyelectrolytes on the viscosity when one inorganic salts added * The viscosities were at 15i6 ° ö using a Brookfield viscometer and a spindle No. 1 and a spindle Hr * 2 (both 10 rpm). The results are shown in Table 6, using the solutions of polymers B and C of Example 2 became.

Table 6 concentration
of the polymer
(Wt%) Viscosity in
pure water
(Centipoise) viscosity
in 3%
watery
Sodium Chloride
rid (gentleman
poise) Viscosity in
3% aq
rigen Hatrium
BUlÄt
(Oentipoise) polymer 0.1
0.2
0.3
0.25
0.5
0.75 680
1340
1860
225
475
870 10
17th
30th
6th
10
10 10
22nd
36
10
21
47 σ
σ
C.
B.
B.
B.

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Claims (1)

- 19 -patent claims 1. agglomerates, characterized * that they contain a finely ground mineral, an effective slope of a largely straight-chain, water-soluble polymer and water, wherein the polymer has a molecular weight of 300,000 to 25,000 QOO. 2. agglomerates according to claim 1 _S, characterized in that the polymer has a molecular weight τοη 1 000 000 to 20,000,000. 3 »agglomerates according to claim 1, characterized in that that the polymer is a water-soluble polyelectrolyte. 4. agglomerates according to claim 3, characterized in that that the polymer is selected from the following: polyacrylic acid; Polymethacrylic acid; MLschpolyere iron acrylamide, acrylonitrile or ethyl acrylamide with acrylic acid or methacrylic acid; the sodium salts of copolymers τοη maleic acid with styrene or methyl vinyl ether; synthetically modified Starch polymers; Sodium salt of carboxymethyl cellulose, Polymers containing amino groups; Polydimethylaminoethyl methacrylate; and polymers containing quaternary ammonium groups contain. 5. Agglomerates according to claim 1, characterized in that they contain an inorganic salt. 6. agglomerates according to claim 5β, characterized in that that the inorganic salt consists of sodium chloride, sodium sulfate or potassium chloride. 109887/1776 7 agglomerates according to claim 1, characterized in that that they are 0.0004-5 to 4.5 *! kg of polymer per ton (0.001 to 10 lbs. of polymer per clay) contain finely ground mineral. β. Agglomerates according to claim 7 *, characterized in that that si © 0.0045 - 2.27 kg of polymer ^ e ton (0 · 01 - 5 lbs. of polymer per clay) contain finely ground mineral 9 agglomerates according to claim 8, characterized in that that they contain 0.009 - 0.91 kg of polymer ^ per ton (0.02 - 2 lbs. of polymer pen? clay) contain finely ground mineral 10. agglomerates according to claim 1, characterized in that that the finely ground mineral consists of iron oxide ore with a particle size of 10 to 1000 / ^ 11 »agglomerate · according to claim 10, characterized in that the iron oxide ore has a size of 20 to 300 / i » 12. A process for the production of agglomerates, characterized in that one has a finely ground mineral an aqueous solution of an effective amount of a high molecular weight, largely straight-chain, water-soluble polymer is mixed and the resulting mixture is treated, to make agglomerates. 13 * The method according to claim 12, characterized in that that da® polymer is dissolved in an aqueous solution of an inorganic salt before it is finely ground Mineral is mixed. 14. The method according to claim 15, characterized in that that the polymer is dissolved in sea water. 109887/1776 15 · The method according to claim 14 »characterized in that that the Eonsentration of the polymer in seawater 0.01 to 1% by weight is 16 * Method according to claim 15, characterized in that that the concentration of the polymer 0.05 to 0.5 wt .- # and that the agglomerates in a pelletizing · device can be made with inclined rotating disc. 109887/1776